The speed and accuracy of the algorithm is significant for the determination of surface tension via pendant drop method. Based on the MATLAB, the first-order algorithm was improved by the coordinate rotation method and the second-order algorithm was developed to eliminate the deviation of the theoretical profile curve. The surface tension of Iso-octane was measured by the pendant drop method to verify those algorithms, which are integrated into the GUI interface to make the experimental process farther rapid and convenient. The arc length of the pendant drop, drop size and the resolution of the drop photo dependence of surface tension were analyzed, respectively. The result shows that the first-order algorithm and the second-order algorithm were calculated with higher speed and accuracy, respectively. In the condition of contracted neck of pendant drop and the picture was shotting at the image resolution of 1280×960, the calculated value fluctuates little and is in good agreement with the literature data as the fitting arc length is selected from 3.8 to 3.85 mm.